Various apparatus have long used a tension-based recoil system that enables a tether or pull cord to be drawn back onto a spool. One of the most common examples of such a device is that of small motor that comprises a “pull-start”. A cord is typically wound concentrically about a containment spool. One end of the cord is typically attached proximate to the inner circumference of the containment spool. When the cord is drawn out off of the spool by pulling its free end, the containment spool rotates. This results in rotational work that may then be conveyed to the crankshaft of a small motor by a one-way clutch mechanism. Once the cord has been drawn to the completion of its cycle, a recoil means that is attached to the containment spool cause the spool to rotate in an opposite direction. This causes the cord to be taken back up onto the containment spool.
Another interesting application for a recoil cord mechanism is the use of the mechanism to tether a user interface device. In many applications, electronic systems need to receive input from and/or present information to a user. By tethering the user interface device, it may be stowed when the user does not need to interact with the electronic system. And, in this stowed position, the recoil mechanism draws the electrical cord back onto the spool so that it, too, is kept out of the way.
Irrespective of the application, a cord that may be pulled from a spool is always susceptible to failure. When the cord that is pulled from the spool reaches the end of its cycle, it typically experiences a sudden impulse of tensile force. This tensile force induces a stress-oriented failure. Where the cord is used for electrical connections, as in the user interface application described above, failure may be catastrophic. In other applications, the failure may also be catastrophic, but the wear and tear experienced by the cord is generally visible before an actual failure occurs. In the electrical connection case, failure of the electrical cord that is used to tether a user interface device may not be detectable by visual inspection.
These types of failures are exceptionally common where the application of the recoil mechanism constitutes use by members of the public. One example of this is an on-aircraft, in-flight entertainment (IFE) system. In this example application, airline passengers are typically provided with a user interface device. This user interface device is generally disposed in the airline seat and may be stowed in a cradle when it is not in use by the passenger. Each time a passenger draws the user interface device from the cradle, the electrical cord used to effect a connection to the IFE system is fatigued at the end of the pull cycle; leading to eventual and inevitable failure.